Use New Relic add_method_tracer with Class methods

add_method_tracer-singleton.rb

class Product < ActiveRecord::Base
  class << self
    # Define a public instance method on the singleton Class named Product
    def get_recommended_for_subscriber(subscriber)
      # ... call some web service, then use find to return a product instance ...
    end

    add_method_tracer :get_recommended_for_subscriber, 'Custom/Product.get_recommended_for_subscriber'
  end

  # Instance methods of Product go here
end